The present invention relates to a process and apparatus for producing very pure alloys, and more particulary to an improved process and apparatus for producing very pure alloys melt-metallurgically in an vacuum melting assembly.
In an known process for producing alloys, the starting material which forms the alloy is melted in an induction crucible, is subjected to a vacuum treatment and subsequently poured into a resistance-heated casting tundish, out of which it is poured upon formation of a certain metallostatic level and reaches an atomizing chamber through, for example, a atomizing system. In this process, especially in the initial phase of the casting, in which the metallostatic level is not yet attained in the casting tundish, ceramic particles of the lining of the induction crucible and slag particles reach the atomizing chamber. The slag particles also reach the atomizing chamber during the final phase or emptying of the casting tundish. Furthermore, in the process, the danger exists that the liquid material will react with the lining of the casting tundish accompanied by formation of further impurities which also reach the final product.
It is also known to melt the starting material which forms the alloy in an induction crucible having an orifice arranged in the floor, wherein the floor opening can be sealed with a corresponding plug arrangement. With this process, the slag particles indeed remain largely on the surface of the melt, yet the danger exists that the sealing arrangement will be damaged not only by the filling of the crucible with the solid starting material, but also that the sealing faces of the sealing arrangement, that is, the sealing part als well as the orifice, will be eroded by the the continual turbulence of the melt produced in the induction crucible.